AbstractThis thesis comprises two parts. Part A of the thesis deals with bioactivity-guided isolation and identification of anticonvulsant constituents from a medicinal plant Delphinium denudatum, which has been used traditionally for the treatment of epilepsy in Pakistan. Acute toxicity studies and LD50 of various extracts obtained from dried roots of this plant carried out by Dr. Mohisn Raza of our research group and Dr. R. J. Delorenzo in the Medical College of Virginia, Virginia Commonwealth University, USA, indicated that the chloroform extracts obtained by us extraction at different pH values as well as their diterpenoid alkaloidal constituents were highly toxic to neuromuscular system of mice. In a joint research program with Dr. R. J. DeLorenzo, the anticonvulsant constituents were found to be localized in the least toxic aqueous extract (A.E), since it showed strong anticonvulsant action both in invitro and in invivo experiments. Bioactivity-guided fractionation of the aqueous extract (A.E.) with various solvents yielded an acetone fraction (FS-1) which was ten times more active than the A.E. in in vitro studies. The acetone fraction (FS-1) showed strong limitation of sustained repectitive firing (SRF) of hippocampal neurons as well as also inhibited pentylenetertrazole (PTZ) and bicucculine (BIC)-induced epileptiform activity in a dose-dependent manner. In in vitro experiments, carried out in USA. FS-1 exhibited strong action in subcutaneous pentylenetetrazole (scPTZ), subcutaneous bicucculine (scBIC) and maximal electroshock (MES) tests, suggesting that the compounds present in FS-1 can be effective in therapy of generalized tonic-clonic, partial, absence and myoclonic seizures. Further purification of the acetone fraction by us yielded several sub-fractions (FSS 15-19) that also showed strong limitation of SRF of hippocampal neurons in culture. Two novel compounds named as delphadiencne 1 (21) and delphadienone II (22) were isolated from these sub-fractions (FSS 15-19) Delphadienone 1 (21) Delphaqienone II (22)